Write a notes on alkali leaching process?

Explanation

In this method ,the ore is treated with aqueous alkali to form a soluble complex.for example,bauxite ,an important ore of aluminium is heated with a solution of sodium hydroxide or bauxite ,an important ore of aluminium is heated with a solution hydroxide or sodium in the temperature range 470-520 K at 35 atm to form soluble sodium meta-aluminate leaving behind the impurities ,iron oxide and titanium oxide.
`Al_(2)O_(3)(S)+2NaOH(aq)+3H_(2)O(l)to2Na[Al(OH)_(4)](aq)`
The hot solution is decanted ,cooled ,and diluted .This solution is neutralised by passing `CO_(2)` gas,to the form hydrated `Al_(2)O_(3)` precipitate.
`2Na[Al(OH)_(4)](aq)+CO_(2)(g)toAl_(2)O_(3).xH_(2)O(s)+2NaHCO_(3)(aq)`
The precipitate is filtered off and heated around 1670 K to get pure alumina `Al_(2)O_(3)`